Development of a cyan blue-emitting Ba3La2(BO3)4:Ce3+,Tb3+ phosphor for use in dental glazing materials: color tunable emission and energy transfer

Abstract

The Ce³⁺/Tb³⁺ doped Ba₃La₂(BO₃)₄ phosphors were synthesized by a conventional solid state reaction method. The synthesized phosphor samples are a single phase of Ba₃La₂(BO₃)₄ and showed angular-shaped fine grains with average particle size from 5 μm to 10 μm. The Ba₃La₂(BO₃)₄:Ce³⁺ phosphors showed an asymmetric broad blue emission under excitation at 365 nm and the Ba₃La₂(BO₃)₄:Tb³⁺ phosphors exhibited typical green emission assigned to the 4f–4f transition of Tb³⁺ under excitation at 254 nm. Under near-UV (365 nm) excitation, Ba₃La₂(BO₃)₄:Ce³⁺,Tb³⁺ phosphors showed both a blue emission band and green emission peaks due to Ce³⁺ and Tb³⁺, respectively. By optimizing the composition, cyan-blue emission with high color purity (CIE chromaticity coordinate values x = 0.2557 and y = 0.3839) was obtained for the Ba₃La₂(BO₃)₄:0.05Ce³⁺,0.03Tb³⁺ phosphor, and the internal quantum efficiency of the phosphor at the excitation wavelength of 365 nm is estimated to be 50%. The dental glazing paste prepared by mixing organic binder, Ba₃La₂(BO₃)₄:Ce³⁺,Tb³⁺ phosphors, and low T_g glass was successfully vitrified when it was heated at 600 and 700 °C, and showed high chemical stability of the luminescence properties in acidic aqueous solution (pH = 4).